A urinary catheter is a hollow, partially flexible tube that permits the free passage or drainage of urine from the bladder for external collection via a drainage bag or the like. The catheter is inserted into an individual's bladder via the urethra, effectively short circuiting the anatomy/physiology of the lower urinary tract (i.e., creates a low resistance channel to passively drain the bladder, often to an external urine collection device). The catheter may be one that stays in place throughout the day (i.e., an indwelling urinary catheter commonly characterized by a bladder anchor structure, e.g., an inflatable balloon), or an intermittent catheter which is inserted and removed each time the bladder is drained.
Catheters are utilized for several different clinical reasons such as urinary incontinence (i.e., leaking urine or being unable to control when you urinate), or following lower urinary tract surgery in which the surgeon is looking to avoid filling the bladder and/or having the urine come in contact with the urethra immediately following a medical procedure. More usually, a urinary catheter is utilized when a patient has symptoms of urinary retention (i.e., being unable to empty your bladder when you need to), a medical condition, or surgery. Excessive urine accumulation in the bladder may cause pain, bladder injury and/or reflux of urine through the ureters into the kidneys.
Most catheters are a short term fix (i.e., temporary), necessary only until the ability to self-void can be reliably and safely demonstrated, however, circumstances abound which warrant a lengthy deployment (i.e., chronic).
Each year in the United States, more than a million patients receive an indwelling urinary catheter due to urinary retention. Urinary retention often occurs when the bladder vesical pressure does not adequately overcome the bladder outlet resistance, resulting in an inability to adequately empty the bladder. These episodes are often temporary and the drainage catheter can eventually be removed. Many of these retention events occur in hospitals as a result of temporary impairment of vesical pressure.
Hospitals and urology practices have difficultly predicting when an individual no longer needs a urinary catheter to empty his or her bladder. The use of urinary catheters comes with a high incidence of medical complications, including urinary tract infections, known as catheter associated urinary tract infections (CAUTIs), the most common type of healthcare associated infection. Traditionally, caregivers may have erred on the side of leaving the catheter in too long, resulting in high rates of CAUTIs. The Centers for Disease Control and Prevention (CDC) estimates 13,000 U.S. patient deaths each year due to CAUTIs, an excess length of stay of two to four days, an unnecessary antimicrobial use, and an increased cost of $0.4-0.5 billion nationally per year (“Catheter-associated Urinary Tract Infection (CAUTI) Toolkit,” Carolyn Gould, MD MSCR).
Due to an increased awareness of catheter-related medical complications and various emerging healthcare economic incentives, including financial penalties directly tied to rates of CAUTIs, the protocols for the removal of urinary catheters have become more aggressive and have resulted in increased incidents of bladder injury due to retention events after premature removal of the urinary catheter.
There are a wide range of clinical protocols to determine whether a catheter can be removed, often dependent on place-of-service and whether a urologist is involved in the protocol. These varying protocols commonly involve the removal of the catheter without an assessment of vesical pressure; the bladder is simply allowed to fill, either naturally or artificially, and observations over time as to whether the patient remains in urinary retention are made, with a bladder ultrasound oftentimes used to measure post void residual urine remaining in the bladder. If the patient cannot adequately void, a catheter is again placed in the bladder. This is an expensive protocol, requiring highly organized and lengthy clinical supervision to determine whether the catheter needs to be replaced. Complications of this protocol include inadvertent overfilling of the bladder during retention events (i.e., bladder distention) as well as the known increase in CAUTI risk owing to the process of reinserting a catheter that was prematurely removed.
As was previously referenced, bladder vesical pressure determinations and assessment are important indicators of lower urinary tract functionality, and a critical component of a urodynamic study. The measurement of bladder vesical pressure using a standard indwelling (Foley) drainage catheter deployed for that purpose is currently a gold standard for the diagnosis of intra-abdominal hypertension (IAH) and abdominal compartment syndrome (ACS). Historically, Foley catheters have been specifically deployed and utilized to measure vesical pressure as part of a urodynamics examination for various assessments of bladder dysfunction.
The Foley catheter, named for its designer Boston surgeon Frederic Foley, is by far the most common type of indwelling urinary catheter. For all intents and purposes, the Foley catheter is the standard-of-care device to address retention.
With reference to FIG. 1, Foley catheter 10 generally comprises a body 12 (e.g., tube) characterized by proximal 14 and distal 16 end portions, and two discrete channels or lumens, namely, a drain lumen 18, and an inflation lumen 20 (FIG. 1A).
Proximal portion 14 of tube 12 is characterized by a bifurcation which delimits a drain segment 12A, characterized by lumen 18, and an inflation segment 12B, characterized by lumen 20. Drain segment 12A is adapted for operative union with a urine collection system, commonly a urine collection device and a valve for regulating urine discharge/collection. Inflation segment 12B is adapted to include an inflation valve 22.
Distal portion 16 of tube 12, the insertion end, includes an anchoring structure in the form of an inflatable balloon 24. Balloon 24 is operatively linked to inflation valve 22 via lumen 20 in furtherance of select inflation (i.e., expansion) of the inflatable balloon, commonly with sterile water, once distal end portion 14 is suitably positioned in the bladder. Moreover, distal portion 16 of tube 14 includes a urine ingress port in the form of an aperture 26 in a sidewall of tube 12, with drain lumen 18 terminating at or combining with the aperture so as to delimit and function as a urine conduit, draining urine from the bladder to and into the external collection bag.
In bladder pressure related assessment applications, a standard 2-way or 3-way Foley catheter is placed into the bladder, the former characterized by one balloon fill port and one urine drainage port, the latter by one balloon fill port and two urine drainage ports. Fluid, commonly sterile water, is introduced into the anchoring balloon to enable retention of the device via cooperative engagement of the fluid filled balloon with the bladder outlet/bladder neck.
Depending on the clinical application, the bladder may be artificially filled with fluid, often sterile water, through the drainage line of the catheter. A pressure transducer is connected to the urine drainage line to indicate/measure the vesical pressure. The pressure transducer may be designed to prevent urine from draining through the urine drainage line, thus, a 3-way catheter is often chosen for continuous monitoring as drainage can continue to occur through the primary drainage line.
In the application of the diagnosis of IAH or ACS, continuous monitoring of the vesical pressure provides insight into the state of the intra-abdominal pressure. Typical clinical applications include emergency trauma and acute care surgery patients who are at risk of IAH and resultant organ dysfunction. In the application of assessment of bladder dysfunction, the vesical pressure is often monitored while the bladder is being filled, and when the bladder is emptying through the catheter.
Numerous catheters beyond the basic Foley, and adaptations thereof, have emerged for the assessment of bladder storage anomalies (i.e., incontinence), including attendant devices/systems that enable multifunction operation. More particularly, functionally specific specialty catheters are available to perform urodynamic assessments.
For instance, Rhea, Jr. (U.S. Pat. No. 5,916,153) generally provides a multifunction catheter, more particularly, a Foley catheter adapted to include an integral pressure sensor near the insertion end thereof. The sensor is embedded or molded into the catheter wall, with associated wiring extending from the sensor embedded in the catheter structure.
Neal et al. (U.S. Pat. No. 6,434,418), as Rhea, Jr., likewise provide a multifunction catheter, more particularly, a modified Foley catheter for measuring intrauterine pressure and fetal heart rate. Three embodiments of this specialized catheter are disclosed by Neal et al., each characterized by one or more of a fetal heart rate electrode proximal an insertion end (see Neal et al. FIG. 2), a pressure sensor proximal an insertion end (FIG. 5 (Neal et al.)), or a microphone proximal an insertion end (FIG. 7 (Neal et al.)). A pressure transducer and output device are operatively linked to the catheter for sensing bladder pressure via the anchor balloon and its associated lumen (FIG. 1 (Neal et al.)), or via a dedicated pressure sensor (FIG. 5 or FIG. 7 (Neal et al.)).
Wallace et al. (U.S. Pat. No. 6,447,462) provide a urodynamic catheter system characterized by a small volume, closed air column operatively linking a catheter anchoring balloon with a remote transducer assembly. Provisions for a catheter employing a transducer external to a patient's body which does not rely upon a liquid filled column and which provides an automatic reference pressure is a stated aim.
Tracy (U.S. Pat. No. 7,004,899), in keeping with Rhea, Jr. and/or Neal et al., make use of specially equipped Foley catheters while generally providing a portable self-contained diagnostic system for assessing urinary function characterized by a control device adapted to receive a plurality of testing modules (see FIG. 5, and compare FIGS. 1 & 2). A cystometrogram (CMG) module 1400, characterized by a pressure transducer 128, is contemplated (FIG. 14), tubing of a tubing assembly bonded or welded with/to the specialty catheter, with monitoring of back pressure in a drainage conduit linking the bladder to the transducer, or sensing of bladder pressure with an adapted Foley catheter characterized by a pressure sensor carried by the catheter tip.
Woodruff et al. (U.S. Pat. No. 8,192,368) provide a specialty pressure sensing catheter characterized by a closed, pre-filled fluid (i.e., liquid) system. More particularly, a transducer assembly is permanently affixed to a urethral catheter, a predetermined previously installed charge of fluid extends from the transducer of the transducer assembly through a lumen and to the interior volume of a sensing balloon. Improved sensing accuracy and minimal set up time are stated advantages.
Finally, Burnett et al. (US 2016/0183819) provide specially equipped sensing catheters. More particularly, a dedicated pressure sensing device, such as a balloon 38 (FIG. 5A) or membrane 39 (FIG. 5B), is supplied as part of the catheter system in addition to a retention balloon 36. The dedicated pressure sensing element is contemplated in combination with further sensing elements such as analyte and/or temperature sensors 50, 32.
In-as-much as the specialty catheters have found favor, there is a general and continuing appreciation to leverage an already deployed Foley catheter to secure pressure data. For instance, Goedje et al. (US 2012/0041334) generally disclose a pressure measuring unit for use with a urethral catheter. The unit includes a pressure sensor and essentially plumbing which permits, in the alternative, via select valving of the plumbing, either the sensing of gas pressure in a balloon via a balloon lumen, or sensing of bladder pressure via a bladder lumen. A controller, operatively linked to the pressure measuring unit, is adapted to receive pressure measurement signals from the pressure sensor and to calibrate a calibration of internal balloon pressure relative to the urine/bladder pressure.
Nishtala et al. (U.S. Pat. No. 8,337,411) disclose a variety of bypass devices, for use in combination with clamps or valves, for measuring intra-abdominal pressure (IAP) utilizing an already, as opposed to specifically deployed urethral catheter. Bypass devices are contemplated for connecting to a sampling port of a catheter system (see e.g., FIG. 1A), or to an inflation port of such system (see e.g., FIG. 31A).
Finally, Nishtala (U.S. Pat. No. 8,535,237), in keeping with his earlier work, provides a bypass device (FIG. 3) for operative union with a standard Foley catheter. The device is characterized by, among other things, a valve, a syringe with plunger, and a compression chamber, the device aiding in priming the contemplated intra-abdominal pressure monitoring system and balancing/equilibrating the system.
While device specialization has its place, it remains desirable to leverage the elegant simplicity of the standard indwelling urinary catheter in furtherance of securing urodynamic data. Moreover, stakeholders, e.g., first and foremost patients, as well as care providers, insurers, etc., desire right sizing treatments. Further still, it is believed, especially in the instant context, that, while technologic advances, whether it be more robust sensing or enhanced sensing precision via improved indwelling devices or appurtenant advanced electronics to support same, are welcome, when it comes to basic data gathering, a less-is-more approach characterized by an easy to use system or kit of few elements remains desirable and advantageous. Thus, a system, ideally enabled in a kit format, for quick, reliable, secure integration with a previously deployed indwelling urinary catheter, and further still, a related protocol for determining indwelling catheter removal conditions, is sought.